1. Field of the Invention
The present invention relates to a method and a device for peeling off silicon wafers for semiconductors from a beam to which the silicon wafers after slice processing are bonded via an adhesive, for example.
2. Related art of the Invention
In recent years, as alternative energy to oil, solar photovoltaic generation has been noticed.
In the solar photovoltaic generation, reduction in costs of silicon wafers that are used in bulk is required, so efficient manufacturing of silicon wafers from silicon ingots is now required.
The method for manufacturing silicon wafers comprises, roughly speaking, a bonding step, a slicing step, a rough-washing and peeling-off step, a wafer-separating step, a washing step, and an inspecting step.
Accordingly, referring to FIG. 4, descriptions are given more specifically regarding a conventional method for manufacturing silicon wafers.
Here, FIG. 4 is a schematic front view (the XZ plan view) of a conventional structure body, in which the silicon ingot 1, the beam 2, and the base plate 10 are bonded.
The silicon ingot 1 is monocrystalline or polycrystalline silicon, which is shaped like a round column or a square column. The beam 2 is, in this conventional method for manufacturing silicon wafers, a glass plate that is a protector for preventing fracture of the processing end part of the silicon ingot 1. The base plate 10 is a jig for installation to a device called a wire saw for manufacturing the thin silicon wafers 1a from the silicon ingot 1 by slice processing. The adhesive 8 is, in this conventional method for manufacturing silicon wafers, a two-component liquid.
To begin with, in the bonding step, the adhesive 8 is applied to the silicon ingot 1 or the beam 2 to bond the silicon ingot 1 and the beam 2 and, besides, the adhesive 8 is applied to the beam 2 or the base plate 10 to bond the beam 2 and the base plate 10.
Next, in the slicing step, the slice processing is performed with the wire saw with respect to the silicon ingot 1 that has been bonded to the beam 2 and the base plate 10. The silicon ingot 1 that has become one thousand and several hundred sheets of the silicon wafers 1a by the slice processing is bonded to the beam 2 via the adhesive 8. Usually, the slice processing is performed so that the gaps between the adjacent silicon wafers 1a reach from the side of the silicon ingot 1 to a part of the adhesive 8 and the beam 2 on the side of the silicon ingot 1.
Next, in the rough-washing and peeling-off step, the silicon wafers 1a that are bonded to the beam 2 are washed, and the one thousand and several hundred sheets of the silicon wafers 1a are peeled off from the beam 2 en bloc using hot water of 50° C. for allowing the adhesive 8 to thermally soften, or an agent such as lactic acid and the like as a washing agent.
Next, in the wafer-separating step, the silicon wafers 1a overlapping each other, which have been peeled off from the beam 2 en bloc, are separated one by one so that the silicon wafers 1a are placed apart from each other.
Next, in the washing step, the silicon wafers 1a that have been separated are washed.
And, in the inspecting step, the silicon wafers 1a that have been washed are inspected.
By the way, in the aforesaid rough-washing and peeling-off step, the one thousand and several hundred sheets of the silicon wafers 1a are peeled off from the beam 2 en bloc as mentioned above.
Because of this, there often arises a state where a silicon wafer 1a that has been peeled off overlaps onto another silicon wafer 1a that has been peeled off, or silicon wafers 1a that have been peeled off fall toward each other.
And, there is a case where the silicon wafer 1a in a state like this cracks, or an edge part of the silicon wafer 1a chips.
Further, since work is necessary such that the silicon wafers 1a, which have been unevenly accumulated in the rough-washing and peeling-off step, are uniformly accumulated by hand to be allowed to move for the next wafer-separating step, or are repacked in a rack for the wafer-separating step, it is feared that efficiency of manufacturing decreases.
Accordingly, a method for peeling off silicon wafers is known such that the silicon wafers 1a are peeled off from the beam 2 one by one while the adhesive 8 is heated by spraying a hot wind in the air from the −Y side, that is, the surface side of the silicon wafer 1a on the outermost side that is to be peeled off (see, for example, Japanese Utility Model Registration Publication No. 3149712).
Further, in the aforementioned method for peeling off silicon wafers, the rough-washing is not performed, and the hot wind is sprayed in a state where the powdery silicon sludge that arises during the slice processing and the processing liquid are mixed together and are choking the gaps between the adjacent silicon wafers 1a. 